Nonpoint source pollution from agriculture represents a major threat to the quality of water in the European Union (EU) context. As part of the implementation process of the EU Water Framework Directive in France, the cooperation between water suppliers and agricultural stakeholders has been recently promoted for limiting diffuse agricultural pollution at the water catchment level. Based on a conceptual framework combining transaction cost economics and the social-ecological system (SES) framework, this paper identifies the conditions under which such collective action is effective for the restoration/maintenance of water quality. The research relies on a cross-case comparison of cooperation in six drinking water catchments. A qualitative analysis of primary data collected at the national, water basin and local levels serves as a basis for the multi-case investigation. Variables related to the hydrogeological system, the stakeholders involved, the contracts governing cooperation and the economic and policy contexts are shown to interact in their influence on collective action. The results highlight the importance of the match between contract incentives and the characteristics of the local context and the potential complementarities between informational, regulatory and economic policy tools for enhancing the effectiveness of collective action for water pollution control.

在欧盟（EU）的背景下，农业的面源污染对水质构成了重大威胁。作为法国《欧盟水框架指令》实施过程的一部分，最近促进了水供应商与农业利益相关方之间的合作，以在集水区限制扩散的农业污染。基于将交易成本经济学和社会生态系统（SES）框架相结合的概念框架，本文确定了在何种条件下这种集体行动对于恢复/维持水质有效。该研究依赖于六个饮用水流域合作的跨案例比较。对国家/地区收集的主要数据进行定性分析，流域和地方层面作为多案调查的基础。与水文地质系统，所涉利益相关者，管理合作的合同以及经济和政策环境有关的变量在影响集体行动方面相互影响。结果强调了合同激励机制与当地环境特征之间的匹配的重要性以及信息，监管和经济政策工具之间潜在的互补性，以增强水污染控制集体行动的有效性。